Interfacing a conditional access circuit to a digital device using input and output stream switching

ABSTRACT

The present invention is a method and apparatus for interfacing a host and a conditional access circuit to a digital device. A switching circuit is coupled to the host and the conditional access circuit to switch input streams into output streams. The input streams include a host stream from the host and the output streams include an interface output stream. An interface circuit is coupled to the steering circuit and the digital device to transfer the interface output stream to the digital device.

BACKGROUND

[0001] 1. Field of the Invention

[0002] The present invention is related to conditional access devices.In particular, the present invention is related to interfacing aconditional access device to a digital device.

[0003] 2. Description of Related Art

[0004] Modern set-top boxes generally have a receiver to receive programdata, or content, from a service provider and generate multipletransport streams. The content is normally scrambled before beingtransmitted to the receiver. The scrambled content is then de-scrambledby a conditional access (CA) device. Currently, entitlement managementmessages (EMM) typically use unique keys or signatures to deliver agroup key or access parameters to CA devices. An EMM is a message usedto deliver privileges (e.g., rights, keys) to a CA device. Typically thegroup are users or customers who share a particular set of entitlements.The National Renewable Security System (NRSS) defines two types of CAdevices or modules: an NRSS part A module supporting a smart card formfactor, and an NRSS part B module supporting a PCMCIA form factor.

[0005] The unscrambled content is then transferred or downloaded to adigital device such as a display device (e.g., digital television) forprogram viewing or a recording device (e.g., digital video cassetterecorder) for program recording. In many scenarios, multiple digitaldevices are connected to the conditional access device for simultaneousactivities such as viewing while recording or viewing at differentdisplay locations.

[0006] A standardized interface between the conditional access deviceand the digital device is desirable. However, it is important tosafeguard the content or transport streams from unauthorized copying bythe digital device. In addition, the interface should be flexible enoughto accommodate several usage options such as store and playback.

[0007] Therefore, there is a need to have an efficient and flexibletechnique to interface a conditional access device to a digital device.

SUMMARY

[0008] The present invention is a method and apparatus for interfacing ahost and a conditional access circuit to a digital device. A switchingcircuit is coupled to the host and the conditional access circuit toswitch input streams into output streams. The input streams include ahost stream from the host and the output streams include an interfaceoutput stream. An interface circuit is coupled to the steering circuitand the digital device to transfer the interface output stream to thedigital device.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The features and advantages of the present invention will becomeapparent from the following detailed description of the presentinvention in which:

[0010]FIG. 1 is a diagram illustrating a system in which one embodimentof the invention can be practiced.

[0011]FIG. 2 is a diagram illustrating a digital receiver and a decoderaccording to one embodiment of the invention.

[0012]FIG. 3 is a diagram illustrating a conditional access systemaccording to one embodiment of the invention.

[0013]FIG. 4A is a diagram illustrating a switching circuit according toone embodiment of the invention.

[0014]FIG. 4B is a diagram illustrating another switching circuitaccording to one embodiment of the invention.

[0015]FIG. 4C is a diagram illustrating a switching circuit with are-scrambler according to one embodiment of the invention.

DESCRIPTION

[0016] The present invention is a method and apparatus to interface ahost and a conditional access circuit to a digital device. A switchingcircuit is coupled to the host and the conditional access circuit toswitch input streams into output streams. The input streams include ahost stream from the host. The output streams include an interfaceoutput stream. An interface circuit is coupled to the switching circuitand the digital device to transfer the interface output stream to thedigital device. The conditional access circuit includes a de-scramblerand a copy protection circuit. The de-scrambler receives a de-scramblerinput stream and generates a de-scrambled stream. The output streamsfurther include a copy stream to the copy protection circuit and thede-scrambler input stream to the descrambler. The input streams furtherinclude the de-scrambled stream from the de-scrambler and an interfaceinput stream from the interface circuit.

[0017] In one embodiment, the switching circuit comprises a firstswitching element coupled to the host and the de-scrambler to providethe interface output stream from an internal stream and the de-scrambledstream; and a second switching element coupled to the digital device,the copy protection circuit and the de-scrambler to provide the copystream from the de-scrambled stream and the interface input stream.

[0018] The switching and interface circuit provides flexibility in datarouting for input and output streams to support a variety of platforms,configurations, or environments.

[0019] In the following description, numerous specific details are setforth in order to provide a thorough understanding of the presentinvention. It will be apparent, however, to one of ordinary skill in theart that the present invention may be practiced without these specificdetails. In other instances, well-known architectures, steps, andtechniques have not been shown where unnecessary for an understanding ofthe present invention. For example, specific details are not provided asto whether the method is implemented in a station as a software routine,hardware circuit, firmware, or a combination thereof. The term “stream”refers to a transport stream which is typically in a digital form.

[0020]FIG. 1 is a diagram illustrating a system 100 in which oneembodiment of the invention can be practiced. The system 100 includes aprogram data receiver 110, a transmission medium 120, an audio system130, a digital video recorder or player 140, a disk recording unit 150,a display 160, a control unit 170, and a network CA unit 180. Any of theaudio system 130, the digital video recorder or player 140, the diskrecording unit 150, the display 160 and the control unit 170, or anycombination thereof may be referred to as a digital device.

[0021] The program data receiver 110 includes a digital receiver 112 anda decoder 114. The digital receiver 112 receives digital bitstream ordata including program data from one or more service providers. Suchservice or content providers may include terrestrial broadcasters, cableoperators, direct broadcast satellite (DBS) companies, companiesproviding content for download via the Internet, book publisher,software companies distributing software products, or any similarcontent and/or service provider. The program data may include systeminformation, entitlement control messages, entitlement managementmessages, content, and other data. System information may includeinformation on program names, time of broadcast, source, method ofretrieving and decoding, copy management commands that provide digitalreceivers and other devices that control how, when, and what programdata may be replayed, retransmitted, copied, and/or recorded. These copymanagement commands may also be transmitted along with entitlementcontrol messages (ECM), which are generally used by the conditionalaccess unit to regulate access to a particular channel or service.Entitlement management messages (EMM) may be used to deliver privilegessuch as rights and de-scrambling keys. As known, a decryption orde-scrambling key is generally a code that is required to restore thescrambled data, and may be a function of the rights granted. Finally,content in the program data may include audio and video data, which maybe in s scrambled or encrypted or clear format. In one embodiment, theprogram data receiver 110 is a television set where the digital receiver112 is a set-top box integrated therein, and the decoder 114 is a MotionPicture Experts Group (MPEG) decoder.

[0022] The transmission medium 120 operates to transmit controlinformation and data including program data between the program datareceiver 110 and other components in the system 100. The transmissionmedium 120 may include air, fiber optics, electronic and magnetic media,computer network connection, telephone connection, and any othercommunication media.

[0023] The audio system 130 is coupled to the transmission medium 130 toprovide audio services. The audio system 130 may include speakers, anaudio player/recorder such as a compact disk player, or othermagneto-optical disc that may be used to play and/or record audio data.The digital video recorder/player 140 is coupled to the transmissionmedium 120 to provide video services. The digital video recorder/player140 may be used to record analog or digital video, audio, and other datatransmissions. In one embodiment, the digital video recorder/player 140may be used to replay or record the program data received by the programdata receiver 110 and transmitted over the transmission medium 120.

[0024] The disk recording unit 150 may also be coupled to the programdata receiver 110 and other components via the transmission medium 120.The disk recording unit 150 may be a personal computer system, astand-alone hard disk recording unit, or other disk recording devicecapable of recording analog or digital audio, video and datatransmissions, including the program data received and transmitted bythe program data receiver 110.

[0025] The display 160 may include a television display, a monitordisplay or other devices capable of processing and displaying videosignals. In one embodiment, the display 160 is a digital television set.The control unit 170 may also be coupled to the transmission medium 120to coordinate and control the operation of some or each of thecomponents on the system 100, as well as other devices remotely coupledthereto.

[0026] The network conditional access (CA) unit 180 may also be coupledto the transmission medium 120. The network CA unit 180 operates tore-scramble program data with content in clear format such that thesystem 100 supports the simultaneous transmission of program data inclear and scrambled format. The network CA unit 180 may be a CA devicethat operates as a second CA device in a system embodiment where theprogram data receiver 110 operates as a master CA device.

[0027]FIG. 2 is a diagram illustrating a digital receiver 112 accordingto one embodiment of the invention. The digital receiver 112 includes acentral processing unit (CPU) 210, a tuner 220, a demodulator 230, aconditional access (CA) unit 240, and a demultiplexer 250.

[0028] The control processing unit 210 performs control functions forthe tuner 220, the CA unit 240 and the demultiplexer 250. The CPU 210may determine the frequency in which a channel is broadcast or otherwisetransmitted. The CPU 210 may support a graphical user interface (GUI),such as electronic programming guide (EPG) to allow a user to navigatethrough various channels and program options to select a desired channelor program for viewing, listening, recording and the like.

[0029] The tuner 220 selects a frequency of the signal received by theprogram data receiver 110 (in FIG. 1) under the control of the CPU 210.The tuner 220 processes, amplifies, digitizes, and generates a bitstreamto the demodulator 230.

[0030] The demodulator 230 demodulates the bitstream received from thetuner 220 to provide the program data as originally transmitted. Thetype of demodulation performed by the demodulator 230 depends on thetype of transmission as well as the modulation process used in thetransmission process. Examples of the demodulation includes quadratureamplitude modulation (QAM) demodulation, quadrature phase shift key(QPSK) demodulation, and vestigial side band (VSB) demodulation. Inaddition, the demodulator 230 may perform error correction on thereceived bitstream.

[0031] The conditional access unit 240 may be integral or external tothe digital receiver 112. The CA unit 240 provides conditional access tothe program data as provided by the demodulator 230. The program data istypically scrambled using an access key. The CA unit 240 may be used inan external or split mode. In the external mode, the CA unit 240de-scrambles the program data content and decrypts the keys externally;e.g., as is the case with the National Renewable Security System (NRSS)conditional access modules. In a split conditional access unit, theprogram data content is de-scrambled within the digital receiver 112,while the key decryption is done externally, e.g., via a smart card.

[0032] The demultiplexer 250 receives the de-scrambled or unscrambledcontent from the CA unit 240. The demultiplexer 250 separates the systeminformation from the content in the program data, and according to oneembodiment, parses the program data for packet identifiers that areassociated with the system information, audio information, and videoinformation, and then transmits the system information to the controlprocessing unit 210 and the audio and video information to the decoder114 (in FIG. 1).

[0033] When the CA device 240 is used externally to the digital receiver112, the digital receiver 112 is typically referred to as a host. In thefollowing, a host is used to describe a digital receiver or any deviceor system that can provide a transport stream to the CA device. Adigital device is any one of the audio system 130, the digital videorecorder or player 140, the disk recording unit 150, the display 160 andthe control unit 170 (shown in FIG. 1), or any combination thereof.

[0034]FIG. 3 is a diagram illustrating a conditional access (CA) device240 according to one embodiment of the invention. The CA device 240includes a switching and interface circuit 310, a CA circuit 320, a CAprocessor 330, and a smart card interface 340.

[0035] The switching and interface circuit 310 is coupled to the host,the CA circuit 320 and the digital device to provide interface betweenthe CA device 240 and the digital device. The switching and interfacecircuit 310 includes a switching circuit 312 and an interface circuit314. The CA circuit 320 scrambles a stream and generates acopy-protected stream to the host. The CA circuit 320 includes a copyprotection circuit 322 and a de-scrambler 324.

[0036] The switching circuit 312 is coupled to the host and the CAcircuit 320 to switch input streams into output streams. The inputstreams include a host stream from the host, a de-scrambled stream fromthe de-scrambler 324, and an interface input stream from the interfacecircuit 314. The output streams include an interface output stream tothe interface circuit 314, a de-scrambler input stream to thede-scrambler 324, and a copy stream to the copy-protection circuit 322.

[0037] The interface circuit 314 is coupled to the switching circuit 310and a digital device to transfer the interface output stream from theswitching circuit 310 to the digital device and the interface inputstream from the digital device to the switching circuit 310. Theinterface circuit 314 convert the interface output stream into thecorresponding interface protocol, and the stream from the digital deviceinto the proper stream to the switching circuit 310. In one embodiment,the interface protocol is the 1394 serial interface protocol. Thedigital device may be any one of the audio system 130, the digital videorecorder or player 140, the disk recording unit 150, the display 160 andthe control unit 170 (shown in FIG. 1), or any combination thereof. Itis contemplated that the digital device has a corresponding interfacecompatible with the interface circuit 314, e.g., supporting the sameinterface protocol.

[0038] The de-scrambler 324 receives and de-scrambles the de-scramblerinput stream from the switching circuit 310 to generate the de-scrambledstream. The de-scrambler 324 receives the control and a de-scramblingkey from the CA processor 330.

[0039] The copy protection circuit 322 receives the copy stream from theswitching circuit 312 and generates a copy protected stream to the host.In general, the host then receives a de-scrambled and copy-protectedstream from the CA device 300.

[0040] The CA processor 330 provides control and coordination ofconditional access operations. The CA processor 330 may also providescontrol to the switching circuit 312 to control the switching or dataselection functions. The smart card interface 340 provides interface tothe smart card. In one embodiment, the smart card interface 340 is thePCMCIA card interface.

[0041] The switching circuit 312 provides a number of switching methodsto the input streams to the output streams. Alternative embodimentsexist to provide several data paths for the streams to be routed orsteered within the switching circuit 312.

[0042]FIG. 4A is a diagram illustrating a switching circuit 312Aaccording to one embodiment of the invention. The switching circuit 312Aincludes a first switching element 410 and a second switching element420.

[0043] The first switching element 410 receives the host stream from thehost and the de-scrambled stream from the de-scrambler 324 (shown inFIG. 3). The host stream may be in a scrambled or clear format. Thefirst switching element 410 generates an internal stream, and generatesthe de-scrambler input stream to the de-scrambler 324 and the interfaceoutput stream to the interface circuit 314.

[0044] The first switching element 410 includes a connection to connectthe host stream to the internal stream and the de-scrambler inputstream. In other words, the host stream is the internal stream and alsothe de-scrambler input stream. The first switching element 410 furtherincludes a data selector, or multiplexer, 412. The data selector 412receives at its inputs the host stream and the descrambled stream andprovides the interface output stream. The data selector 412 may becontrolled by the CA processor 330 (in FIG. 3).

[0045] The second switching element 420 includes a data selector 422.The data selector 422 receives at its inputs the interface input streamfrom the interface circuit 314 (in FIG. 3) and the de-scrambled streamfrom the de-scrambler 324 (in FIG. 3), and generates the copy stream tothe copy protection circuit 322 (in FIG. 3). The data selector 422 maybe controlled by the CA processor 330 (in FIG. 3).

[0046] The first and second switching elements 410 and 420 provideflexible data routing for the input and output streams. A number ofscenarios exist. For example, the host stream may be in scrambled formatand is routed to the descrambler 324. The de-scrambler 324 de-scramblesthe scrambled host stream. The data selector 412 then selects thede-scrambled host stream to the interface output stream. The interfaceoutput stream is the host stream in the clear format. The interfacecircuit 314 then sends the clear host stream to the digital device suchas a digital television for displaying the original content. In anotherscenario, the host stream may be in the clear format and can bedelivered directly to the interface output stream via the data selector412. The digital device may provide a return path of a clear stream tothe switching element 420 to be sent to the copy protection circuit 322.The copy protection circuit 322 then provides a copy protected stream tothe host.

[0047]FIG. 4B is a diagram illustrating a switching circuit 312Baccording to one embodiment of the invention. The switching circuit 312Bincludes the first and second switching elements 410 and 420 (in FIG.4A) and a third switching element 430.

[0048] The third switching element 430 includes a data selector 432. Thedata selector 432 receives the internal stream from the first switchingelement 410 and the interface input stream from the interface circuit314 (in FIG. 3), and provides the de-scrambler input stream to thede-scrambler 324 (in FIG. 3). The third switching element 430 may becontrolled by the CA processor 330 (in FIG. 3).

[0049] The first, second, and third switching elements 410, 420, and430, provide further flexible data routing for the input and outputstreams. With the addition of the third switching element 430, thede-scrambler input stream may be taken from the host stream or from thereturn stream provided by the digital device. The return stream from thedigital device may be scrambled and is de-scrambled by the de-scrambler324.

[0050]FIG. 4C is a diagram illustrating a switching circuit 312Caccording to one embodiment of the invention. The switching circuit 312Cincludes the first, second, and third switching elements 410, 420, and430 (in FIG. 4B), a fourth switching element 440, and a scrambler 450.

[0051] The fourth switching element 440 includes a data selector 442.The data selector receives the host stream and a scrambled stream fromthe scrambler, and generates the internal stream to the first switchingelement 410. The fourth switching element 440 may be controlled by theCA processor 330 (in FIG. 3).

[0052] The scrambler 450 receives the de-scrambled stream from thedescrambler 324 and provides the scrambled stream to the fourthswitching element 440. The scrambler 450 may act as a re-scrambler forthe return stream from the digital device.

[0053] The first, second, third, and fourth switching elements 410, 420,430, and 440, and the scrambler 450 provide further flexibility in datarouting for the input and output streams. A number of scenarios exist.For example, a “store and playback” scheme can be supported which allowsa scrambled content, either from the broadcast stream from the host orlocally scrambled, to be recorded or played back through the switchingand interface circuit. For example, a scrambled content may be providedby a digital device via the interface input stream. The scrambledcontent is then de-scrambled by the de-scrambler 324 via the switchingelement 430. This de-scrambled content is then re-scrambled by thescrambler 450 and goes through the switching elements 440 and 410 to theinterface circuit 314. The re-scrambled content is then transferred tothe same or different digital device via the interface circuit 314. Atthe same time, the de-scrambled content can be copy protected by thecopy protection circuit via the switching element 420 and sent to thehost.

[0054] While this invention has been described with reference toillustrative embodiments, this description is not intended to beconstrued in a limiting sense. Various modifications of the illustrativeembodiments, as well as other embodiments of the invention, which areapparent to persons skilled in the art to which the invention pertainsare deemed to lie within the spirit and scope of the invention.

What is claimed is:
 1. An apparatus to interface a conditional accesscircuit to a digital device, the apparatus comprising: a switchingcircuit coupled to a host and the conditional access circuit to switchinput streams into output streams, the input streams including a hoststream from the host, the output streams including an interface outputstream; and an interface circuit coupled to the switching circuit andthe digital device to transfer the interface output stream to thedigital device.
 2. The apparatus of claim 1 wherein the host stream isin one of scrambled and clear formats.
 3. The apparatus of claim 2wherein the conditional access circuit includes a de-scrambler and acopy protection circuit, the de-scrambler receiving a de-scrambler inputstream and generating a de-scrambled stream.
 4. The apparatus of claim 3wherein the output streams further include a copy stream to the copyprotection circuit and the de-scrambler input stream to thede-scrambler.
 5. The apparatus of claim 4 wherein the input streamsfurther include the de-scrambled stream from the de-scrambler and aninterface input stream from the interface circuit.
 6. The apparatus ofclaim 5 wherein the switching circuit comprises: a first switchingelement coupled to the host and the de-scrambler to provide theinterface output stream from an internal stream and the de-scrambledstream; and a second switching element coupled to the digital device,the copy protection circuit and the de-scrambler to provide the copystream from the descrambled stream and the interface input stream. 7.The apparatus of claim 6 wherein the internal stream provides thede-scrambler input stream and wherein the host stream provides theinternal stream.
 8. The apparatus of claim 6 further comprising: a thirdswitching element coupled to the first switching element, the digitaldevice and the de-scrambler to provide the de-scrambler input stream tothe de-scrambler from the host stream and the interface input stream. 9.The apparatus of claim 8 further comprising: a fourth switching elementcoupled to the first and third switching elements to provide theinternal stream from the host stream and a scrambled stream; and ascrambler coupled to the fourth switching element and the de-scramblerto provide the scrambled stream from the de-scrambled stream.
 10. Theapparatus of claim 1 wherein the interface circuit provides a 1394serial interface.
 11. A method to interface a conditional access circuitto a digital device, the apparatus comprising: switching input streamsinto output streams by a switching circuit coupled to a host and theconditional access circuit, the input streams including a host streamfrom the host, the output streams including an interface output stream;and transferring the interface output stream to the digital device by aninterface circuit.
 12. The method of claim 11 wherein the host stream isin one of scrambled and clear formats.
 13. The method of claim 12wherein the conditional access circuit includes a de-scrambler and acopy protection circuit, the de-scrambler receiving a de-scrambler inputstream and generating a de-scrambled stream.
 14. The method of claim 13wherein the output streams further include a copy stream to the copyprotection circuit and the de-scrambler input stream to thede-scrambler.
 15. The method of claim 14 wherein the input streamsfurther include the de-scrambled stream from the de-scrambler and aninterface input stream from the interface circuit.
 16. The method ofclaim 15 wherein switching comprises: providing the interface outputstream from an internal stream and the de-scrambled stream by a firstswitching element; and providing the copy stream from the de-scrambledstream and the interface input stream by a second switching element. 17.The method of claim 16 wherein the internal stream provides thede-scrambler input stream and wherein the host stream provides theinternal stream.
 18. The method of claim 16 further comprising:providing the de-scrambler input stream to the de-scrambler from thehost stream and the interface input stream by a third switching element.19. The method of claim 18 further comprising: providing the internalstream from the host stream and a scrambled stream by a fourth switchingelement; and providing the scrambled stream from the de-scrambled streamby a scrambler.
 20. The method of claim 11 wherein the interface circuitprovides a 1394 serial interface.
 21. A system comprising: a host toprovide a content; a conditional access device coupled to the host toprovide conditional access to the content, the condition access devicehaving a conditional access circuit; a digital device coupled to theconditional access device to access the content; and a circuit coupledto the host and the digital device to provide interface between theconditional access device and the digital device, the circuitcomprising: a switching circuit coupled to the host and the conditionalaccess circuit to switch input streams into output streams, the inputstreams including a host stream from the host, the output streamsincluding an interface output stream, and an interface circuit coupledto the switching circuit and the digital device to transfer theinterface output stream to the digital device.
 22. The system of claim21 wherein the host stream is in one of scrambled and clear formats. 23.The system of claim 22 wherein the conditional access circuit includes ade-scrambler and a copy protection circuit, the de-scrambler receiving ade-scrambler input stream and generating a de-scrambled stream.
 24. Thesystem of claim 23 wherein the output streams further include a copystream to the copy protection circuit and the de-scrambler input streamto the de-scrambler.
 25. The system of claim 24 wherein the inputstreams further include the de-scrambled stream from the de-scramblerand an interface input stream from the interface circuit.
 26. The systemof claim 25 wherein the switching circuit comprises: a first switchingelement coupled to the host and the de-scrambler to provide theinterface output stream from an internal stream and the descrambledstream; and a second switching element coupled to the digital device,the copy protection circuit and the de-scrambler to provide the copystream from the descrambled stream and the interface input stream. 27.The system of claim 26 wherein the internal stream provides thede-scrambler input stream and wherein the host stream provides theinternal stream.
 28. The system of claim 26 wherein the switchingcircuit further comprises: a third switching element coupled to thefirst switching element, the digital device and the de-scrambler toprovide the de-scrambler input stream to the de-scrambler from the hoststream and the interface input stream.
 29. The system of claim 28wherein the switching circuit further comprises: a fourth switchingelement coupled to the first and third switching elements to provide theinternal stream from the host stream and a scrambled stream; and ascrambler coupled to the fourth switching element and the de-scramblerto provide the scrambled stream from the de-scrambled stream.
 30. Thesystem of claim 21 wherein the interface circuit provides a 1394 serialinterface.